Carrier-wave signaling



April .12, 1927.

CARRIER WAVE Filed April R. C. MATHES SIGNALING Riffw76 um.i g

/m/mor.y Faber/CIMM@ Patented Apr. 12, 1927.

UNITED STATES PATENT OFFICE'.

ROBERT C. MATHES, OF WYOMING, NEW JERSEY. ASSIGNOR, BY MESNE ASSIGNMNTS,TO 'WESTERN ELECTRIC COMPANY, INCORPORATED, A CORPORATION OF NEW YORK.

CARRIER-WAVE SIGNALING.

Application led April 3, 1925. Serial No. 20,376.

This invention relates to carrier wave Signaling and particularly tomultiplex carrier telegraph receiving circuits.

An ob'ect of the invention is to provide an efficient and economicalmultiplex carrier current telegraph system.

A related object of the .invention is to obtain a high degree ofselectivity between various message waves employed in systems of thistype, with an accompanying economy in the frequency range.

From an economic standpoint, it is desirable in multiplex carriercurrent telegraph systems to include as large a number of signalingchannels as possible within a given frequency range. The closeness ofspacing of the frequencies assigned to the various channels depends uponthe frequency range needed for the desired quality of telegraph signals.and to a large extent upon the frequency separation of the bands neededto provide for selectivity. The range of the individual channelfrequencies, of course, cannot be reduced without impairing the qualityof the telegraph signals. In accordance with the present invention,however, the frequency spacing between the individual channelfrequencies is materially reduced, thus rendering available additionalsignaling channels within a given frequency range.

This is accomplished by so arranging the output circuit of eachreceiving channel that interfering impulses from adjacent receivingchannels are neutralized. A portion of the output of each receivingchannel is passed through auxiliary windings on the receiving relays ofthe adjacent channels. The auxiliary windings are so proportioned and sopoled that the current therein will just annul the effects of theinterfering currents in the main windings of the relays which are due tointerfering impulses from the adjacent channels. y

A particular advantage of the invention is that it may be applied to astandard audio frequency or high frequency carrier telegraph systemwithout otherwise altering the system where cross-talk exists which itis desired to reduce or eliminate.

The invention will be described in connection with the accompanyingdrawing which is a diagrammatic illustration of the west terminalstation of a multiplex carrier current telegraph system embodying theinvention.

The usual east terminal station, which is identical to the west stationshown in the drawing, is omitted for the sake of simplifying theshowing. The drawing shows only so much of the Morse telegraph equipmentas is necessary to a complete understanding of the invention,thisequipment being similar to that shown in Fig. of the article byMessrs. Golpitts and Blackwill entitled Garrier current telephony andtelegraphy published in the Transactions of the American Institute ofElectrical En gineers, vol. 40, 1921.

The terminal circuits include a plurality of transmitting channels TG1,TG2, etc., connected to a common transmitting circuit TL, and aplurality. of receiving channels RGl, RC2, etc., connected to a commonreceiving circuit RL. The common transmitting circuit TL and the commonreceiving circuit RL are coupled to the multiplex transmission line MLby means of the usual hybrid coil H and balancing network N.

Garrier currents are utilized for transmission over the line ML and aregrouped as to their frequencies, the higher frequencies as a group beingused for transmission from west to east, and the lower frequencies as agroup being used for transmission from east to west.

Each transmitting channel includes a source of carrier waves, a circuitfor controlling the carrier waves by signal impulses, and a selectivecircuit. These channels are identical in construction and hencereference will be made only to the apparatus of channel TG1.

The outgoing channel TG1 comprises an oscillator O1, a sending key T,Land a transmitting selective circuit TSG1. These elements are shown indetail in Figure 55 of the ,Golpitts and Blackwell article, supra. Ifdesired, the selective circuit TSGl, however, may be either a resonantcircuit such as is shown in the Golpitts and Blackwell article, or maybe a band filter of the type disclosed in Patent No. 1,227,113 to G. A.

Gampbell, issued May 22, 1917. The oscillators Ol, O2, etc. are adaptedto generate carrier currents of the different frequencies which areassigned to the respective transmitting channels.

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Normally, the output circuit of the oscillator O, is open at the contactolf sending .key l`,. When the key l1 is depressed, however, a carriervvave of the :frequency assigned to the channel TC, is transniittedthrough selective circuit TSQ, common transmitting circuit TL andhylirid coil ll to the multiplex transmission line ML. Carrier Waves otthe frequencies assigned to the other transmitting channelsv are.similarly impressed upon the liuc ML,

Each receiving channel includes a receiving selective circuit, adetector and amplitier. and a receiving relay. These channels aie allidentical except, of course, that the constants ot' the selectivecircuits diti'er to the extent necessary to accommodate the ditlerent'frequency carrier Waves employed.

The receiving channel RQ, tor example, comprises a receiving selectivecircuit RSC, which may he a resonant circuit or a hand lilter` adetecter-amplilier fl)i\ and a rcceiving relay Rp These elements areshown in detail in .Figure 55 ot the Colpitts and Blackwell article,supra. The channel RC, also includes a loiv pass lilter l?, for apurpose hereinatter to he described.

Carrier currents incoming over the line Alli are transmitted through thehyhrid coil .ll to the. common receiving circuit RTL Where they arepicked up h v the respective .ser lectivo circuits tor transmission tothe proper channels. (lui-rents ot the trequency assigned to channel RG,t'or example, are transmitted through selective circuit RSC, and areamplitied and detected in the detector-amplilier DAI. The rectifiedcurrents are transmitted through filter F, and caused to actuatereceiving relay Rp llhcn currents ot' the tretpiency assigned to channelRC, are impressed upon the eommon receiving circuit; RL, not only is aresponse produced in the appropriate relay lL, hut a portion ot thiscurrent is also transmitted through the selective circuit RSG2 which isnext adjacent the selective circuit RSU, in the Frequency scale. Theseinter- `teringl currents` when rectified` may be sntlicient to cause thetalse operation oli the relay ll., in the receiving channel RCL.. Thesame conditions apply to the, other receiving channels ot" the svsten'i.

The necessityv t'or eliminatingl such inter 'tering currents hasheretofore imposed severe requirements on the receiving selectivecircuits, thus inaterially increasing the cost ot these circuits. lt hasalso heen customary to provide a itairly ivide separation lietn'een the,'trequcncy hands assigned to the respective channels. thus utilizing aconsideralile portion ot the availalile tieuucnev range which mightotherwise lie used tor additional signaling channels. ln accordance withthe present invention. lif'nvever. the outrcceiving chan` put circuitsot the respective nels are so arranged that interfering i111- pnlsestrom adjacent channels are neutralized.

The relay lt, in addition to its main winding` .l is provided 'with anauxiliary or neulralizing winding- 2 connected in the output ot' channelRC2. The relay RL., .in addition to its main winding t in the outputcircuit; ot channel lith, is provided ivith two auxilianvv winding incircuit, respectively, with the output circuits oliI the channels nextadjacent thereto in the 'frequency scale. The auxiliar)Y orneutralizingwinding` 3 ot relay lt2 is connected in thc output circuitol' channel RQ, uhile the auxiliary winding 5 is connected in the outputcircuitk o'l channel litt, ln this ivay, a measured portion ot theoutput ot each receiving channel is iinpiessed upon an auxiliary windingof the respective receiving relays in the output circuits ot' theadjacent channels. The anx iliary windings 2, l, 5, ete., are soproportioned and so poled that the currents therein will just aimul theetl'eets ot the .interfering currents ivhich are impressed upon the main\\-indings 1, t, etc., ot the receiving relays.

When several trcqucucies are impressed upon the common receiving circuitRL at the same time, the inain current andthe intel-tering currents ineach channel may produce heats in the detectors at a frequency equal to'the trequency ot separation, which .might tend to ieduee theetteetiveness ot' the interterence neutral' The beat treization.quent-ies. however, may lie suppressed from transmission to thereceiving relays hy in- .serting a single section otE a` low pass litterin the output ot the detectors. These filters, l F2, ctc.. may he oit'the type disclosed in the (.iamphell patent, supra.

lhe invention set toi-th herein is, of course, susceptihle ot variousother modifications and :ulaptations not specifically referred to, hatincluded within the scope ot the appended Claims.

lllhat, is claimed is:

l. In a multiplex carrier Wave signaling s vstein. a circuit t'orreceiving carrier Waves ot' ditlerent frequencies, a plurality ofreceiving' channels associated therewith, a tiuinslating device in eachof said channels controlled in accordance with Waves oi a particulartrequeney, and means associated with the translating` device of eachchannel tor preventing the actuation thereof by Waves ot anotherilrequency.

2. ln a multiplex carrier wave signaling` system, a circuit torreceiving signal-modulated carrier 'aves ot' ditlerent frequencies, zplurality ot receiving channels each including a translating deviceassociated with said circuit. means in each ot said channels 'tortransmitting i'iiutually exclusive hands ot treuucncies, and n'ieansassociated vvitli the translatingl device of each channel for lucneutralizing the effect of interfering Waves of frequencies assigned toadjacent channels.

In a multiplex carrier wave signaling system, a circuit for receivingcarrier waves ot' different frequencies, a plurality of receivingchannels associated therewith, and a receiving i'elay in each of saidchannels having a winding connected with an adjacent channel.

4. In a multiplex carrier wave signaling system, a circuit for receivingcarrier waves of different frequencies, a plurality of receivingchannels associated therewith, a selective circuit in each of saidchannels adapted to transmit a particular band of frequencies and togreatly attenuate frequencies outside said band, a detector in each ofsaid channels, and a receiving relay in the output of the detector ineach of said channels having a winding connected with an adjacentchannel.

5. In a multiplex carrier wave signaling system, a circuit for receivingsignal-inodulated carrier waves of different frequencies, a plurality ofreceiving channels associated therewith, selective circuits fortransmitting mutually exclusive bands of frequencies to said channels, adetector in each of said channels, a receiving relay in each of saidchannels having a main winding in the output of the detector therein,and auxiliary windings on said relays connected in the output of thedetectors of adjacent channels, said auxiliary windings being so piopor-,tioiied and so poled that the current therein will just annul theeffects of interfering currents in the main windings of said relays.

(S. In a multiplex carrier wave signaling system, a circuit forreceiving carrier waves of different frequencies,

a plurality of rceeiving channels each including a translating deviceassociated with said circuit, a selective circuit in each of saidchannels adapted to transmit a particular band of frequencies and togreatly attenuate frequencies outside said band, and means associatedWith each of said channels for neutralizing the effect of interferingwaves of frequencies assigned to another channel.

7. In a multiplex carrier wave signaling sysein, a circuit for receivingcarrier Waves of different frequencies, a plurality of receivingchannels each including a translating device associated with saidcircuit, a selective circuit in each of -said channels adapted totransmit a particular band of frequencies and to greatly attenuatefrequencies outside said band, and means associated with eachtranslating device for insuring against the operation thereof by anycurrents from said circuit having frequencies adapted to operateadjacent translating devices.

8. In a multiplex signaling system, a transmission line for receivingcurrents of different frequencies, a plurality of selective receivingcircuits connected to said line and each having a translating devicetherein, each of said channels being adapted to transmit a particularband of frequencies and to greatly attenuate frequencies outside saidband, interconnecting means between said translating devices forinsuring against the operation of each translating device by currents ofthe frequencies received through the associated channel from the lineand adapted to operate adjacent translating devices.

In witness whereof, I hereunto subscribe my naine this 2 day of April A.D., 1925.

ROBERT C. MATHES.

